Semiconductor device and method of manufacturing the same

ABSTRACT

In a method of manufacturing a semiconductor device, the semiconductor device includes a non-volatile memory formed in a memory cell area and a ring structure area surrounding the memory cell area. In the method, a protrusion of a substrate is formed in the ring structure area. The protrusion protrudes from an isolation insulating layer. A high-k dielectric film is formed, thereby covering the protrusion and the isolation insulating layer. A poly silicon film is formed over the high-k dielectric film. The poly silicon film and the high-k dielectric film are patterned. Insulating layers are formed over the patterned poly silicon film and high-k dielectric film, thereby sealing the patterned high-k dielectric film.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of application Ser. No. 15/698,469filed on Sep. 7, 2017, which claims priority to U.S. Provisional PatentApplication 62/439,739 filed Dec. 28, 2016, the entire disclosure ofeach of which is incorporated herein by reference.

TECHNICAL FIELD

The disclosure relates to semiconductor integrated circuits, moreparticularly to semiconductor devices including non-volatile memorycells and peripheral devices, and manufacturing processes thereof.

BACKGROUND

As the semiconductor industry has progressed into nanometer technologyprocess nodes in pursuit of higher device density, higher performance,and lower costs, there have been challenges in controlling flatness ofan underlying layer in view of lithography operations. A flash memoryutilizing non-volatile memory (NVM) cells has continually been scaleddown and is embedded in advanced CMOS logic integrated circuits (ICs)for a smart card and automotive applications. In particular, integrationof manufacturing processes for the NVM cells and manufacturing processesfor peripheral logic circuits become more complex and important.

BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure is best understood from the following detaileddescription when read with the accompanying figures. It is emphasizedthat, in accordance with the standard practice in the industry, variousfeatures are not drawn to scale and are used for illustration purposesonly. In fact, the dimensions of the various features may be arbitrarilyincreased or reduced for clarity of discussion.

FIG. 1A shows a plan view (a layout) and FIG. 1B shows a cross sectionalview, illustrating one stage of a sequential manufacturing process of asemiconductor device according to embodiments of the present disclosure.

FIG. 2 shows a cross sectional view illustrating one stage of asequential manufacturing process of a semiconductor device according toembodiments of the present disclosure.

FIG. 3 shows a cross sectional view illustrating one stage of asequential manufacturing process of a semiconductor device according toembodiments of the present disclosure.

FIG. 4 shows a cross sectional view illustrating one stage of asequential manufacturing process of a semiconductor device according toembodiments of the present disclosure.

FIG. 5 shows a cross sectional view illustrating one stage of asequential manufacturing process of a semiconductor device according toembodiments of the present disclosure.

FIG. 6 shows a cross sectional view illustrating one stage of asequential manufacturing process of a semiconductor device according toembodiments of the present disclosure.

FIG. 7 shows a cross sectional view illustrating one stage of asequential manufacturing process of a semiconductor device according toembodiments of the present disclosure.

FIG. 8 shows an enlarged cross sectional view illustrating a memory cellarea according to some embodiments of the present disclosure.

FIG. 9 shows a cross sectional view illustrating one stage of asequential manufacturing process of a semiconductor device according toembodiments of the present disclosure.

FIG. 10 shows a cross sectional view illustrating one stage of asequential manufacturing process of a semiconductor device according toembodiments of the present disclosure.

FIG. 11A shows a plan view (a layout) and FIG. 11B shows a crosssectional view, illustrating one stage of a sequential manufacturingprocess of a semiconductor device according to embodiments of thepresent disclosure.

FIG. 12 shows a cross sectional view illustrating one stage of asequential manufacturing process of a semiconductor device according toembodiments of the present disclosure.

FIG. 13 shows a cross sectional view illustrating one stage of asequential manufacturing process of a semiconductor device according toembodiments of the present disclosure.

FIG. 14 shows an enlarged cross sectional view illustrating a ringstructure area according to embodiments of the present disclosure.

FIG. 15 shows a plan view (a layout) illustrating one stage of asequential manufacturing process of a semiconductor device according toother embodiments of the present disclosure.

FIG. 16 shows a cross sectional view illustrating a ring structure areaaccording to other embodiments of the present disclosure.

FIG. 17 shows an enlarged cross sectional view according to otherembodiments of the present disclosure.

FIG. 18 shows a cross sectional view illustrating a ring structure areaaccording to other embodiments of the present disclosure.

FIG. 19 shows an enlarged cross sectional view according to otherembodiments of the present disclosure.

FIG. 20 shows a cross sectional view illustrating a ring structure areaaccording to other embodiments of the present disclosure.

FIG. 21 shows an enlarged cross sectional view according to otherembodiments of the present disclosure.

DETAILED DESCRIPTION

It is to be understood that the following disclosure provides manydifferent embodiments, or examples, for implementing different featuresof the invention. Specific embodiments or examples of components andarrangements are described below to simplify the present disclosure.These are, of course, merely examples and are not intended to belimiting. For example, dimensions of elements are not limited to thedisclosed range or values, but may depend upon process conditions and/ordesired properties of the device. Moreover, the formation of a firstfeature over or on a second feature in the description that follows mayinclude embodiments in which the first and second features are formed indirect contact, and may also include embodiments in which additionalfeatures may be formed interposing the first and second features, suchthat the first and second features may not be in direct contact. Variousfeatures may be arbitrarily drawn in different scales for simplicity andclarity.

Further, spatially relative terms, such as “beneath,” “below,” “lower,”“above,” “upper” and the like, may be used herein for ease ofdescription to describe one element or feature's relationship to anotherelement(s) or feature(s) as illustrated in the figures. The spatiallyrelative terms are intended to encompass different orientations of thedevice in use or operation in addition to the orientation depicted inthe figures. The device may be otherwise oriented (rotated 90 degrees orat other orientations) and the spatially relative descriptors usedherein may likewise be interpreted accordingly. In addition, the term“made of” may mean either “comprising” or “consisting of.”

In the present embodiment, a semiconductor device includes non-volatilememory (NVM) cells and peripheral devices (e.g., logic circuits). TheNVM cells generally use a stacked structure in which plural layers, suchas polysilicon layers, are stacked, while the peripheral devicesgenerally include field effect transistors (FETs) having a singlepolysilicon layer. In various embodiments of the present disclosure, aring structure (a guard ring) made by an active region (diffusionregion) is provided for at least the NVM area.

FIG. 1A shows a plan view (a layout) and FIG. 1B shows a cross sectionalview, illustrating one stage of a sequential manufacturing process of asemiconductor device according to some embodiments of the presentdisclosure. FIG. 1B shows a cross sectional view along the line X1-X1 ofFIG. 1A, which illustrates one stage of the semiconductor manufacturingprocess according to some embodiments of the present application. FIG. 2shows a cross sectional view along the line X1-X1 in the area A1 of FIG.1A. Similarly, FIGS. 3-7, 9, 10, 11B, 12 and 13 are cross sectionalviews corresponding to the line X1-X1 in the area A1 of FIG. 1A. In someembodiments, an NVM ring structure labeled as MR surrounds the NVM cellarray area MA and a peripheral ring structure area LR surrounds theperipheral logic circuit are LA, as shown in FIG. 1A.

In some embodiments, prior to fabricating the NVM cells and theperipheral devices (e.g., transistors), a substrate in the NVM cell areais etched to make a “step” between the NVM cell area and the peripheraldevice area. The step height corresponds to the height difference whenan interlayer dielectric (ILD) layer is formed if the step is otherwisenot formed. In the following embodiments, the step height is notillustrated for simplicity.

As shown in FIGS. 1A and 1B, a pad oxide layer 12 is formed on thesubstrate 10 and a nitride layer 14 is further formed on the pad oxidelayer 12. In an embodiment, the substrate 10 includes silicon. Thesubstrate 10 is, for example, a p-type silicon substrate with animpurity concentration being in a range from about 1×10¹⁵ cm⁻³ and about5×10¹⁵ cm⁻³. In other embodiments, The substrate includes an n-typesilicon substrate with an impurity concentration being in a range fromabout 1×10¹⁵ cm⁻³ and about 5×10¹⁵ cm⁻³.

Alternatively, the substrate 10 may comprise another elementarysemiconductor, such as germanium; a compound semiconductor includingGroup IV-IV compound semiconductors such as SiC and SiGe, Group III-Vcompound semiconductors such as GaAs, GaP, GaN, InP, InAs, InSb, GaAsP,AlGaN, AlInAs, AlGaAs, GaInAs, GaInP, and/or GaInAsP; or combinationsthereof. In an embodiment, the substrate 10 includes a silicon layer ofan SOI (silicon-on insulator) substrate. Amorphous substrates, such asamorphous Si or amorphous SiC, or insulating material, such as siliconoxide may also be used as the substrate 10. The substrate 10 may includevarious regions that have been suitably doped with impurities (e.g.,p-type or n-type conductivity).

The pad oxide layer 12 includes thermally grown silicon oxide, and thenitride layer 14 includes silicon nitride (SiN). The silicon oxide andthe silicon nitride can be formed by using a furnace or chemical vapordeposition (CVD), or other suitable film formation operations. Thethickness of the pad oxide layer 12 is in a range from about 5 nm toabout 20 nm and the thickness of the nitride layer 14 is in a range fromabout 50 nm to about 100 nm in some embodiments.

By using a patterning operation, the pad oxide layer 12 and the nitridelayer 14 are patterned into a mask pattern. By using the mask pattern asan etching mask, the substrate 10 is trench etched, and then aninsulating material is formed in the trench, thereby forming isolationinsulating layers (shallow trench isolation) 15 (e.g., 15A, 15B and15C). The insulating material for the isolation insulating layer 15 ismade of, for example, silicon dioxide formed by LPCVD (low pressurechemical vapor deposition), plasma-CVD or flowable CVD. In the flowableCVD, flowable dielectric materials instead of silicon oxide aredeposited. Flowable dielectric materials, as their name suggest, can“flow” during deposition to fill gaps or spaces with a high aspectratio. Usually, various chemistries are added to silicon-containingprecursors to allow the deposited film to flow. In some embodiments,nitrogen hydride bonds are added. Examples of flowable dielectricprecursors, particularly flowable silicon oxide precursors, include asilicate, a siloxane, a methyl silsesquioxane (MSQ), a hydrogensilsesquioxane (HSQ), an MSQ/HSQ, a perhydrosilazane (TCPS), aperhydro-polysilazane (PSZ), a tetraethyl orthosilicate (TEOS), or asilyl-amine, such as trisilylamine (TSA). These flowable silicon oxidematerials are formed in a multiple-operation process. After the flowablefilm is deposited, it is cured and then annealed to remove un-desiredelement(s) to form silicon oxide. When the un-desired element(s) isremoved, the flowable film densifies and shrinks. In some embodiments,multiple anneal processes are conducted. The flowable film is cured andannealed more than once. The isolation insulating layer 15 may be SOG,SiO, SiON, SiOCN or fluorine-doped silicate glass (FSG). The isolationinsulating layer 15 may be doped with boron and/or phosphorous. Further,a planarization operation, such as a chemical mechanical polishing (CMP)method, is performed, thereby exposing the nitride layer 14, as shown inFIGS. 1A and 1B.

As shown in FIG. 1A, frame shaped nitride layers 14 surround the memorycell area MA and the logic circuit area LA, respectively. The width W1of the memory cell ring structure MA is in a range from about 20 nm toabout 1000 nm in some embodiments. The width W2 of the logic area ringstructure LR is in a range from about 20 nm to about 1000 nm in someembodiments. The distance S1 of the isolation insulating layer 15A (adistance between the ring structure and the memory cell area) is in arange from about 50 nm to 10000 nm in some embodiments. The distance S2of the isolation insulating layer 15B (a distance between the memorycell ring structure MA and the logic area ring structure LR) is in arange from about 50 nm to 10000 nm in some embodiments. The distance S3of the isolation insulating layer 15C (a distance between the logic arearing structure LR and the logic circuit area LA) is in a range fromabout 20 nm to 10000 nm in some embodiments.

Then, as shown in FIG. 3, a hard mask layer 40 is formed and patternedby lithography and etching operations so as to expose the memory cellarea MA. The hard mask layer 40 is made of, for example, SiN, SiO₂,SiON, SiOC, SiC, or any other suitable material.

Further, as shown in FIG. 4, a first dielectric layer 21 and a firstpolysilicon layer 50 are formed. The first dielectric layer 21 isutilized as a tunnel oxide layer for the NVM cells and is made ofsilicon oxide. The thickness of the first dielectric layer 21 is in arange from about 1 nm to about 50 nm in some embodiments. The firstdielectric layer 21 can be formed by thermal oxidation or CVD.

The first polysilicon layer 50 can be formed by CVD. The thickness ofthe first polysilicon layer 50 as deposited is in a range from about 10nm to about 300 nm in some embodiments. Then, the thickness of the firstpolysilicon layer 50 is reduced by a planarization operation, such as achemical mechanical polishing (CMP) method or an etch-back method, insome embodiments. After the planarization operation, the thickness ofthe first polysilicon layer 50 is in a range from about 10 nm to about200 nm in some embodiments. The first polysilicon layer 50 isappropriately doped with impurities and is utilized for floating gatesof the NVM cells. The polysilicon layer 50 may be replaced with anamorphous silicon layer.

After the blanket layer of the first poly silicon layer 50 is formed, aplanarization operation, such as chemical mechanical polishing (CMP), isperformed as shown in FIG. 5. By the CMP operation, the first polysilicon layer 50 in the peripheral logic circuit area is removed, and inthe ring structure areas, the thickness of the hard mask 40 graduallydecreases toward the memory cell area due to the step between the NVMcell are and the peripheral logic circuit area, as shown in FIG. 5.

Then, an etch-back operation is performed. By the etch-back operation,the thickness of the first poly silicon layer 50 in the memory cell areais further reduced. As shown in FIG. 6, the thickness D1 of the firstpoly silicon layer 50 after the etch-back operation is in a range fromabout 10 nm to about 100 nm in some embodiments.

Further, by using a wet etching operation, such as a HF dippingoperation, the thickness of the isolation insulating layer 15A isreduced, as shown in FIG. 6. The amount of etching D2 of the isolationinsulating layer 15A measured from the upper surface of the substrate 10is in a range from about 5 nm to about 20 nm in some embodiments. It isnoted that the isolation insulating layers 15B and 15C are covered bythe protective layer 40.

Then, the NVM cell structure CS is formed as shown in FIG. 7. FIG. 8shows an enlarged cross sectional view illustrating the NVM cellstructure according to some embodiments of the present disclosure.

Before forming the NVM cell structure CS, the area other than the memorycell area (e.g., peripheral logic circuit area) is covered by aprotective layer, such as SiN. The first polysilicon layer 50 ispatterned by suitable patterning operations, thereby forming floatinggate patterns (FG patterns) FG. A width of the FG pattern FG is in arange from about 20 nm to about 500 nm and a thickness of the FG patternFG is in a range from about 20 nm to about 500 nm, in some embodiments.

After the FG pattern FG is formed, a stacked layer of a first insulatinglayer stack 52, a second polysilicon layer 54 (for a control gate CG)and a second insulating layer 56 for a hard mask is formed over the FGpattern FG. In some embodiments, first insulating layer stack 52includes one or more of a silicon oxide layer and a silicon nitridelayer. The first insulating layer stack 52 can include a siliconoxide-silicon nitride-silicon oxide (ONO) structure, having thicknessesof about 2-50 nm, about 2-90 nm and about 2-50 nm, respectively, in someembodiments. The thickness of the second polysilicon layer 54 is in arange from about 10 nm to about 200 nm, in some embodiments.

The second insulating layer 56 includes silicon nitride having athickness of about 10 nm to about 500 nm in some embodiments. In certainembodiments, the second insulating layer 56 has a stacked structure of asilicon nitride layer having a thickness of about 5 nm to about 100 nm,a silicon oxide layer having a thickness of about 5 nm to 100 nm, and asilicon nitride layer having a thickness of about 10 nm to about 1000nm, in some embodiments. These layers can be formed by CVD.

Subsequently, the stacked layer is patterned in some embodiments byusing lithography and etching operations, thereby forming a gate stackstructure including the first insulating layer 52, a control gate CG andthe second insulating layer 56, as shown in FIG. 8.

Further, first sidewall spacers 64 (CG spacers) are formed on opposingmain side faces of the stacked gate structure, as shown in FIG. 8. Thefirst sidewall spacers 64 are made of, for example, one or more layersof SiN, SiO₂ and SiON, and have a thickness in a range from about 2 nmto about 100 nm in some embodiments. In some embodiments, the firstsidewall spacers 64 include a silicon oxide-silicon nitride-siliconoxide (ONO) structure, having thicknesses of about 2-100 nm, about 2-100nm and about 2-100 nm.

Further, a diffusion layer 70 and an oxide layer 68 are formed betweentwo gate structures, and second sidewall spacers 58 (FG spacers) areformed as shown in FIG. 8. The second sidewall spacers 58 are made of,for example, one or more layers of SiN, SiO₂ and SiON, which may be thesame or different from the first sidewall spacers, and have a thicknessin a range from about 5 nm to about 100 nm in some embodiments.

Subsequently, word lines 60 (select gate SG) and an erase gate line 66(EG) are formed as shown in FIG. 8. In some embodiments, before formingthe word line, a gate dielectric layer 62, such as silicon oxide or anyother suitable dielectric material, is formed. The word lines SG and theerase gate line EG are made of a conductive material, such as dopedpolysilicon. A thickness of the word lines SG and erase gate line EG isin a range from about 10 nm to about 200 nm in some embodiments.Further, third sidewall spaces (word line WL spacers) may be formed onsidewalls of the word lines SG.

Further, an etch-stop layer 72 and a memory cell protecting layer 74 areformed over the NVM cells as shown in FIG. 8. The etch-stop layer 72 ismade of, for example silicon oxide, and the protecting layer 74 is madeof, for example, silicon nitride, silicon oxynitride, poly silicon oramorphous silicon, in some embodiments.

Subsequently, as shown in FIG. 9, the hard mask layer 40, the nitridelayer 14 and the pad oxide layer 12 in the ring structure and theperipheral logic circuit area are removed, by one or more etchingoperations. By these etching operations, the isolation insulating layers15A, 15B, 15C are partially removed. In the ring structure area, theisolation insulating layer height is reduced, thereby forming asubstrate protrusion PT. The depth D3 above the isolation insulatinglayer 15A from the top of the protrusion PT is in a range from about 5nm to about 50 nm in some embodiments. The depth D4 above the isolationinsulating layer 15B from the top of the protrusion PT is smaller thanD3 and is in a range from about 4 nm to about 49 nm in some embodiments.In other words, a thickness of the isolation insulating layer 15Aadjacent to the protrusion PT and located closer to the memory cell areais smaller than a thickness of the isolation insulating layer 15Badjacent to the protrusion PT and located farther to the memory cellarea. Further, the isolation insulating layer 15C protrudes from thesubstrate in an amount D5 in a range from about 0.5 nm to about 30 nm insome embodiments.

Subsequently, a high-k dielectric film 80 and a poly silicon film 85 areformed as shown in FIG. 10. The high-k dielectric film 80 is formed inthe ring structure area, thereby covering the protrusion PT and theisolation insulating layers 15A, 15B and 15C, and in the peripheralarea. The high-k dielectric film 80 is subsequently used as a gatedielectric layer for the logic circuit. The high-k dielectric film 80 ismade of an oxide of at least one element selected from the groupconsisting of Hf, Y, Ta, Ti, Al and Zr. The high-k dielectric film 80includes HfO₂, HfSiO, HfSiON, HfTaO, HfTiO, HfZrO, zirconium oxide,yttrium oxide, tantalum oxide, aluminum oxide, titanium oxide, hafniumdioxide-alumina (HfO₂—Al₂O₃) alloy, other suitable high-k dielectricmaterials, and/or combinations thereof. In certain embodiments, HfO₂ isused. The high-k dielectric film 80 can be formed by CVD or atomic layerdeposition (ALD). The thickness of the high-k dielectric film 80 is in arange from about 1 nm to about 10 nm in some embodiments. Further, aninterfacial layer (e.g., a chemical oxide or rapid thermal oxide) isformed before the high-k dielectric film 80 is formed.

The poly silicon film 85 is subsequently used as gate electrodes for thelogic circuit. The thickness of the poly silicon film 85 is in a rangefrom about 10 nm to about 200 nm in some embodiments.

Then, as shown in FIGS. 11A and 11B, patterning operation is performedto form the gate structure having a gate dielectric layer 80 and a gateelectrode 85 in the peripheral logic circuit area, as shown in FIG. 11B.FIG. 11A shows a plan view (a layout) and FIG. 11B shows a crosssectional view, corresponding to the line X1-X1 in the area A1 of FIG.11A. Although one gate electrode 85 is shown in the peripheral logiccircuit area, this is merely an illustration for simplicity, and morethan one gate electrodes with various dimensions are disposed in theperipheral logic circuit area.

In the NVM ring structure area MR, the high-k dielectric films 80A and80B are formed on the sides and part of the top of the substrateprotrusion PT to cover the corners of the protrusion PT. The polysilicon layers 85A and 85B are further disposed on the high-k dielectriclayers 80A and 80B respectively. The poly silicon layer in theperipheral logic circuit area and the ring structure area MR can bepatterned at the same time. Accordingly, no extra photo lithographyoperations are required.

As shown in FIG. 11A, the poly silicon pattern has a frame shape, and aninner frame pattern 85B covering the inner edge of the ring structure MRand an outer frame pattern 85A covering the outer edge of the ringstructure MR are formed with a space S1 therebetween. The width W3 ofthe inner frame pattern is in a range from about 10 nm to about 5000 nmand the width W4 of the outer frame pattern is in a range from about 10nm to about 5000 nm, in some embodiments. The width W3 may be the sameas or different from the width W4. The space S1 between the inner framepattern and the outer frame patterns is in a range from about 15 nm toabout 800 nm in some embodiments.

In the ring structure LR of the peripheral logic circuit area LA, nopoly silicon layer and no high-k dielectric layer remains in thisembodiment.

Further, as shown in FIG. 12, the etch-stop layer 72 and the memory cellprotecting layer 74 are removed, and then, sidewall spacers 90A and 90Bare formed on the poly silicon layers 85A and 85B and on sides of thehigh-k dielectric layers 80A and 80B. By the sidewall spacers 90A and90B, the high-k dielectric layers 80A and 80B are sealed together withthe poly silicon layers 85A and 85B. The sidewall spacers 90A and 90Bare made of one or more layer of silicon oxide, silicon nitride andsilicon oxynitride. The thickness W5 of the sidewall spacers 90A and 90B(see, FIG. 14) is in a range from about 2 nm to about 50 nm in someembodiments. The height D6 (see, FIG. 14) of the poly silicon layers 85Aand 85B and the sidewall spacers 90A and 90B from the upper surface ofprotrusion PT is in a range from about 5 nm to about 2000 nm in someembodiments. Sidewall spacers are also formed on sides of the selectgates in the memory cell area.

In the logic circuit area, sidewall spacers 90 are formed on opposingsides of the gate electrode 85 and sides of the gate dielectric layer80, as shown in FIG. 12.

Subsequently, a source/drain implantation is performed to formsource/drain diffusion regions 95 in the logic circuit area LA and cellregion MA. At the same time or by another implantation operation, theimpurities are implanted into the space between the inner and outerframe patterns, where the substrate 10 is exposed, thereby forming adiffusion region 95A, as shown in FIG. 13. FIG. 14 shows an enlargedcross sectional view illustrating the memory cell ring structure. Theimpurities for the diffusion region 95A is BF₂, P, As and/or Sb. Whenthe substrate 10 includes a p-type substrate, the diffusion region 95Ais implanted by p-type impurities for applying substrate bias. Thediffusion region 95A is formed in a frame shape, as a guard ring toelectrically protect the memory cell area MA. In the device operation,the guard ring has the electrically same potential as the substrate inthe memory cell area. In some embodiments, the impurities are alsoimplanted into the logic area ring structure LR, thereby forming a guardring to electrically protect the logic circuit area LA. Further, in someembodiments, an interfacial layer 82, 82A and 82B (e.g., a chemicaloxide or rapid thermal oxide) is formed before the high-k dielectricfilm 80 is formed (see, FIGS. 18 and 19) to improve interface property.In addition, in certain embodiments, a capping layer 86, 86A and 86B isformed between the poly silicon gate layers 85, 85A and 85B and high-kdielectric layers 80, 80A and 80B (see, FIGS. 20 and 21). The cappinglayer is made of, for example, TiN or TaN.

Further, as shown in FIG. 14, an interlayer dielectric (ILD) layer 100is formed over the structures of FIG. 13. The high-k dielectric layersin the memory cell ring structure are physically separated from the ILDlayer 100 by the sidewall spacers 90A and 90B. In some embodiments, anetch stop layer (ESL) made of SiN is formed before forming the ILD 100.In such a case, the high-k dielectric layers in the memory cell ringstructure are physically separated from the ESL by the sidewall spacers90A and 90B.

In some embodiments, the structure shown in FIG. 14 undergoes furtherCMOS processes to form various features such as interconnect vias,interconnect metal layers, passivation layers, etc.

In the foregoing embodiments, in the ring structure LR of the peripherallogic circuit area LA, no poly silicon layer and no high-k dielectriclayer remains in this embodiments. However, in other embodiments, aframe shaped pattern of the poly silicon layer and high-k dielectriclayer is formed on at least one of an outer edge and an inner edge ofthe ring structure LR for the logic circuit area. FIG. 15 shows anembodiment in which a frame shaped pattern of poly silicon 85C is formedon the outer edge (the step between the silicon substrate and theisolation insulating layer 15B) of the ring structure LR. Further, asshown in FIG. 16, a residual high-k dielectric layer 80C is sealed bythe poly silicon layer 85C and the sidewall spacers 90C. In otherembodiments, both the inner edge and the outer edge of the ringstructure LR are covered by frame shaped poly silicon layer andsidewalls, respectively. If the interfacial layer is formed as shown inFIGS. 18 and 19, the residual high-k dielectric layers 80A and 80B aresealed by the poly silicon layers 85A and 85B and the interfacial layers82A and 82B.

Further, the foregoing methods and structures can be applied to any stepwhere a high-k dielectric residue is formed.

FIG. 17 shows an enlarged cross sectional view around the steps betweenthe memory cell ring structure and the logic area ring structureaccording to other embodiments of the present disclosure. In thisembodiment, the step ST is formed by the isolation insulating layer 15.Due to various design and/or process requirements, one or more portionsof the semiconductor device include such a step structure. When the stepheight Dx exceed, for example, about 15 nm (e.g., 15 nm to 30 nm (or 50nm)), a high-k dielectric residue is likely formed as an exposedsidewall, if no poly silicon cover layer is formed. If the interfaciallayer and the capping layer are formed as shown in FIGS. 20 and 21, theresidual high-k dielectric layers 80A and 80B are sealed by the cappinglayers 86A and 86B and the interfacial layers 82A and 82B.

However, by forming a poly silicon cover layer 85X to cover the edge ofthe step ST and by forming sidewall spacers 90X, the high-k dielectricresidue 80X can be sealed from the ILD layer 100.

The step ST may be formed by various elements of the semiconductordevice, such as the isolation insulating layer, the substrate and/or adummy pattern, and such a step is formed before forming the high-kdielectric layer. It is noted that the step height (Dx) may not exceedabout 300 nm in some embodiments. Further, it is noted that the polysilicon cover layer 85X generally has a frame or a ring shapesurrounding another element, but the poly silicon cover layer 85X mayhave a bar shape.

In some embodiments, a metal gate structure using a gate replacementtechnology is employed. In some embodiments, similar to the foregoingembodiments, the poly silicon layers disposed over the high-k dielectriclayers in the ring structure is not replaced with a metal gatestructure. In other embodiments, the poly silicon layer disposed overthe high-k dielectric layer in the ring structure is replaced with ametal gate structure. In certain embodiments, the poly silicon layerdisposed over the high-k dielectric layer in the ring structure ispartially or fully converted into a silicide layer.

It will be understood that not all advantages have been necessarilydiscussed herein, no particular advantage is required for allembodiments or examples, and other embodiments or examples may offerdifferent advantages.

As set forth above, the high-k dielectric layers 80A and 80B are made ofmetal oxide. If the high-k dielectric material remains exposed, metalcontamination may occur in the subsequent manufacturing operation. Forexample, a high-k dielectric residue may be formed in the sidewall ofthe ring structure (protrusion), because of the large step height offsetbetween the protrusion and the isolation insulating layer. With theforegoing operations and structures, the high-k dielectric layers 80Aand 80B are sealed and the metal contamination can be prevented.Further, peeling of the high-k dielectric residue can also be preventedby the method and structures of the present disclosure.

According to one aspect of the present disclosure, in a method ofmanufacturing a semiconductor device, the semiconductor device includesa non-volatile memory formed in a memory cell area and a ring structurearea surrounding the memory cell area. In the method, a protrusion of asubstrate is formed in the ring structure area. The protrusion protrudesfrom an isolation insulating layer. A high-k dielectric film is formed,thereby covering the protrusion and the isolation insulating layer. Apoly silicon film is formed over the high-k dielectric film. The polysilicon film and the high-k dielectric film are patterned. Insulatinglayers are formed over the patterned poly silicon film and high-kdielectric film, thereby sealing the patterned high-k dielectric film.In an embodiment, the protrusion surrounds the memory cell area in planview. In an embodiment, the high-k dielectric film is made of an oxideof at least one element selected from the group consisting of Hf, Y, Ta,Ti, Al and Zr. In an embodiment, a thickness of the isolation insulatinglayer adjacent to the protrusion and located closer to the memory cellarea is smaller than a thickness of the isolation insulating layeradjacent to the protrusion and located farther from the memory cellarea. In an embodiment, the poly silicon film and the high-k dielectricfilm are patterned such that edges of the protrusion are covered by thepatterned poly silicon film and high-k dielectric film. In anembodiment, the poly silicon film and the high-k dielectric film arepatterned such that a center portion of the protrusion is exposed. In anembodiment, the patterned high-k dielectric film is sealed such that anupper surface of the patterned high-k dielectric film is covered by thepatterned poly silicon film and side faces of the patterned high-kdielectric film are covered by the insulating layers. In an embodiment,the insulating layers are made of at least one selected from the groupconsisting of silicon dioxide, silicon nitride and silicon oxynitride.In an embodiment, the protrusion is formed by filling a first trench anda second trench formed in a substrate with an insulating material,reducing a thickness of the insulating material in the first trenchwhile maintaining a thickness of the insulating material in the secondtrench, and further reducing the thickness of the insulating material inthe first trench and reducing the thickness of the insulating materialin the second trench, thereby forming the protrusion protruding from theisolation insulating layer formed in the first and second tranches.

According to one aspect of the present disclosure, in a method ofmanufacturing a semiconductor device, the semiconductor device includesa non-volatile memory formed in a memory cell area, a logic circuitformed in a peripheral area and a ring structure area separating thememory cell area and the peripheral area. In the method, a memory cellstructure is formed. A protrusion of a substrate is formed in the ringstructure area, which protrudes from isolation insulating layers. Ahigh-k dielectric film is formed in the ring structure area, therebycovering the protrusion and the isolation insulating layers, and in theperipheral area. A poly silicon film is formed over the high-kdielectric film. The poly silicon film and the high-k dielectric filmare patterned, thereby forming a gate structure in the peripheral area,and a ring structure in the ring structure area. Insulating sidewallspacers are formed on opposing sides of the gate structure in theperipheral area and sides of the ring structure. In the ring structurearea, the patterned high-k dielectric layer is sealed by the patternedpolysilicon layer and the insulating spacers. In an embodiment, beforethe high-k dielectric film is formed, the memory cell structure iscovered by a protective layer. In an embodiment, the protrusionsurrounds the memory cell area in plan view. In an embodiment, thehigh-k dielectric film is made of an oxide of at least one elementselected from the group consisting of Hf, Y, Ta, Ti, Al and Zr. In anembodiment, a thickness of the isolation insulating layer adjacent tothe protrusion and located closer to the memory cell area is smallerthan a thickness of the isolation insulating layer adjacent to theprotrusion and located farther from the memory cell area. In anembodiment, the ring structure includes an inner ring structure coveringan inner edge of the protrusion and an outer ring structure covering anouter edge of the protrusion. In an embodiment, the inner ring structureis separated from the outer ring structure by an insulating layer. In anembodiment, the patterned high-k dielectric film is sealed such that anupper surface of the patterned high-k dielectric film is covered by thepatterned poly silicon film and side faces of the patterned high-kdielectric film are covered by the insulating layers. In an embodiment,the insulating layers are made of at least one selected from the groupconsisting of silicon dioxide, silicon nitride and silicon oxynitride.

According to one aspect of the present disclosure, a semiconductordevice includes a non-volatile memory formed in a memory cell area of asubstrate, a logic circuit formed in a peripheral area of the substrate,a ring structure surrounding the memory cell area and separating thememory cell area from the peripheral area, and an interlayer dielectric(ILD) layer disposed over the ring structure. The ring structureincludes a first frame shaped poly silicon layer, a first dielectriclayer disposed between the first frame shaped poly silicon layer and thesubstrate, and first sidewall spacers formed on sides of the first frameshaped poly silicon layer. The first dielectric layer is physicallyseparated from the ILD layer by the first sidewall spacers. In anembodiment, a second frame shaped poly silicon layer surrounds the firstframe shaped poly silicon layer.

The foregoing outlines features of several embodiments or examples sothat those skilled in the art may better understand the aspects of thepresent disclosure. Those skilled in the art should appreciate that theymay readily use the present disclosure as a basis for designing ormodifying other processes and structures for carrying out the samepurposes and/or achieving the same advantages of the embodiments orexamples introduced herein. Those skilled in the art should also realizethat such equivalent constructions do not depart from the spirit andscope of the present disclosure, and that they may make various changes,substitutions, and alterations herein without departing from the spiritand scope of the present disclosure.

What is claimed is:
 1. A semiconductor device including: a first ringstructure disposed over a substrate; and an interlayer dielectric (ILD)layer disposed over the first ring structure, wherein: the first ringstructure includes: a first isolation insulating layer disposed in afirst trench formed in the substrate; a first frame shaped poly siliconlayer; a first dielectric layer disposed between the first frame shapedpoly silicon layer and the substrate and between the first frame shapedpoly silicon layer and the first isolation insulating layer; and firstsidewall spacers formed on sides of the first frame shaped poly siliconlayer, and the first dielectric layer is physically separated from theILD layer by the first sidewall spacers.
 2. The semiconductor device ofclaim 1, further comprising a second ring structure surrounding thefirst ring structure, wherein: the ILD layer is disposed over the secondring structure, the second ring structure includes: a second frameshaped poly silicon layer surrounding the first frame shaped polysilicon layer; a second dielectric layer disposed between the secondframe shaped poly silicon layer and the substrate; and second sidewallspacers formed on sides of the second frame shaped poly silicon layer,and the second dielectric layer is physically separated from the ILDlayer by the second sidewall spacers.
 3. The semiconductor device ofclaim 2, wherein the first dielectric layer and the second dielectriclayer are made of a same material.
 4. The semiconductor device of claim3, wherein the same material is a high-k dielectric material made of anoxide of at least one element selected from the group consisting of Hf,Y, Ta, Ti, Al and Zr.
 5. The semiconductor device of claim 2, wherein:the substrate includes a protrusion, the first dielectric layer isdisposed on a top and a first side of the protrusion, and the seconddielectric layer is disposed on the top and a second side of theprotrusion opposite to the first side.
 6. The semiconductor device ofclaim 5, wherein a diffusion region is formed at the protrusion betweenthe first ring structure and the second ring structure.
 7. Thesemiconductor device of claim 5, wherein: the first isolation insulatinglayer is disposed in an inside the ring structure, the semiconductordevice comprises a second isolation insulating layer disposed in asecond trench formed in the substrate in an outside the ring structure,and a thickness of the first isolation insulating layer is smaller thana thickness of the second isolation insulating layer.
 8. Thesemiconductor device of claim 1, wherein: the substrate includes aprotrusion, and the first dielectric layer is disposed on a top and aside of the protrusion.
 9. A semiconductor device including: a memoryformed in a memory cell area of a substrate; a logic circuit formed in alogic circuit area of the substrate; a first ring structure surroundingthe memory cell area and separating the memory cell area from the logiccircuit area; and an interlayer dielectric (ILD) layer disposed over thefirst ring structure, wherein: the first ring structure includes: afirst frame shaped poly silicon layer; a first dielectric layer disposedbetween the first frame shaped poly silicon layer and the substrate; andfirst sidewall spacers formed on sides of the first frame shaped polysilicon layer, and the first dielectric layer is physically separatedfrom the ILD layer by the first sidewall spacers.
 10. The semiconductordevice of claim 9, further comprising a second ring structuresurrounding the memory cell area and separating the memory cell areafrom the logic circuit area, wherein: the ILD layer is disposed over thesecond ring structure, the second ring structure includes: a secondframe shaped poly silicon layer surrounding the first frame shaped polysilicon layer; a second dielectric layer disposed between the secondframe shaped poly silicon layer and the substrate; and second sidewallspacers formed on sides of the second frame shaped poly silicon layer,and the second dielectric layer is physically separated from the ILDlayer by the second sidewall spacers.
 11. The semiconductor device ofclaim 10, wherein the first dielectric layer and the second dielectriclayer are made of a same material.
 12. The semiconductor device of claim11, wherein the same material is a high-k dielectric material made of anoxide of at least one element selected from the group consisting of Hf,Y, Ta, Ti, Al and Zr.
 13. The semiconductor device of claim 10, wherein:the substrate includes a protrusion, the first dielectric layer isdisposed on a top and a first side of the protrusion, and the seconddielectric layer is disposed on the top and a second side of theprotrusion opposite to the first side.
 14. The semiconductor device ofclaim 13, wherein a diffusion region is formed at the protrusion betweenthe first ring structure and the second ring structure.
 15. Thesemiconductor device of claim 13, further comprising: a first isolationinsulating layer disposed in the memory cell area; and a secondisolation insulating layer disposed in the logic circuit area, wherein athickness of the first isolation insulating layer is smaller than athickness of the second isolation insulating layer.
 16. Thesemiconductor device of claim 9, wherein the memory is a non-volatilememory.
 17. The semiconductor device of claim 9, wherein the first ringstructure has a rectangular frame shape.
 18. A semiconductor deviceincluding: a logic circuit formed in a logic circuit area of asubstrate; a ring structure surrounding the logic circuit area; and aninterlayer dielectric (ILD) layer disposed over the ring structure,wherein: the ring structure includes: a frame shaped poly silicon layer;a dielectric layer disposed between the frame shaped poly silicon layerand the substrate; and sidewall spacers formed on sides of the frameshaped poly silicon layer, and the dielectric layer is physicallyseparated from the ILD layer by the sidewall spacers.
 19. Thesemiconductor device of claim 18, wherein the dielectric layer is madeof an oxide of at least one element selected from the group consistingof Hf, Y, Ta, Ti, Al and Zr.
 20. The semiconductor device of claim 18,wherein: the substrate includes a protrusion, the dielectric layer isdisposed on a top and a side of the protrusion, the semiconductor devicefurther includes: a first isolation insulating layer disposed over thesubstrate in an inside of the ring structure; and a second isolationinsulating layer disposed over the substrate in n outside of the ringstructure, and an upper surface of the first isolation insulating layeris higher than an upper surface of the second isolation insulatinglayer.